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Bundle-branch Block
A bundle branch block is a defect in one the bundle branches in the electrical conduction system of the heart. Anatomy and physiology The heart's electrical activity begins in the sinoatrial node (the heart's natural pacemaker), which is situated on the upper right atrium. The impulse travels next through the left and right atria and summates at the atrioventricular node. From the AV node the electrical impulse travels down the bundle of His and divides into the right and left bundle branches. The right bundle branch contains one fascicle. The left bundle branch subdivides into two fascicles: the left anterior fascicle, and the left posterior fascicle. Other sources divide the left bundle branch into three fascicles: the left anterior, the left posterior, and the left septal fascicle. The thicker left posterior fascicle bifurcates, with one fascicle being in the septal aspect. Ultimately, the fascicles divide into millions of Purkinje fibres, which in turn interdigitate with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ejection Fraction
An ejection fraction (EF) is the volumetric fraction (or portion of the total) of fluid (usually blood) ejected from a chamber (usually the heart) with each contraction (or heartbeat). It can refer to the cardiac atrium, ventricle, gall bladder, or leg veins, although if unspecified it usually refers to the left ventricle of the heart. EF is widely used as a measure of the pumping efficiency of the heart and is used to classify heart failure types. It is also used as an indicator of the severity of heart failure, although it has recognized limitations. The EF of the left heart, known as the left ventricular ejection fraction (LVEF), is calculated by dividing the volume of blood pumped from the left ventricle per beat (stroke volume) by the volume of blood collected in the left ventricle at the end of diastolic filling (end-diastolic volume). LVEF is an indicator of the effectiveness of pumping into the systemic circulation. The EF of the right heart, or right ventricular ejection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
First Degree AV Block
First-degree atrioventricular block (AV block) is a disease of the electrical conduction system of the heart in which electrical impulses conduct from the cardiac atria to the ventricles through the atrioventricular node (AV node) more slowly than normal. First degree AV block does not generally cause any symptoms, but may progress to more severe forms of heart block such as second- and third-degree atrioventricular block. It is diagnosed using an electrocardiogram, and is defined as a PR interval greater than 200 milliseconds. First degree AV block affects 0.65-1.1% of the population with 0.13 new cases per 1000 persons each year. Causes The most common causes of first-degree heart block are AV nodal disease, enhanced vagal tone (for example in athletes), myocarditis, acute myocardial infarction (especially acute inferior MI), electrolyte disturbances and medication. The medications that most commonly cause first-degree heart block are those that increase the refractory ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heart Block
Heart block (HB) is a disorder in the heart's rhythm due to a fault in the natural pacemaker. This is caused by an obstruction – a block – in the electrical conduction system of the heart. Sometimes a disorder can be inherited. Despite the severe-sounding name, heart block may cause no symptoms at all in some cases, or occasional missed heartbeats in other cases (which can cause light-headedness, syncope (fainting), and palpitations), or may require the implantation of an artificial pacemaker, depending upon exactly where in the heart conduction is being impaired and how significantly it is affected. Heart block should not be confused with other conditions, which may or may not be co-occurring, relating to the heart and/or other nearby organs that are or can be serious, including angina (heart-related chest pain), heart attack (myocardial infarction), any type of heart failure, cardiogenic shock or other types of shock, different types of abnormal heart rhythms (arrhythmias ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cardiac Pacemaker
350px, Image showing the cardiac pacemaker or SA node, the primary pacemaker within the electrical_conduction_system_of_the_heart">SA_node,_the_primary_pacemaker_within_the_electrical_conduction_system_of_the_heart. The_muscle_contraction.html" "title="electrical conduction system of the heart.">electrical conduction system of the heart">SA node, the primary pacemaker within the electrical conduction system of the heart. The muscle contraction">contraction of cardiac muscle (heart muscle) in all animals is initiated by electrical impulses known as action potentials that in the heart are known as cardiac action potentials. The rate at which these impulses fire controls the rate of cardiac contraction, that is, the heart rate. The cells that create these rhythmic impulses, setting the pace for blood pumping, are called pacemaker cells, and they directly control the heart rate. They make up the cardiac pacemaker, that is, the natural pacemaker of the heart. In most humans, the h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artificial Pacemaker
An artificial cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural cardiac pacemaker) or pacemaker is a medical device that generates electrical impulses delivered by electrodes to the chambers of the heart either the upper atria, or lower ventricles to cause the targeted chambers to contract and pump blood. By doing so, the pacemaker regulates the function of the electrical conduction system of the heart. The primary purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's natural pacemaker is not fast enough, or because there is a block in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow a cardiologist, particularly a cardiac electrophysiologist, to select the optimal pacing modes for individual patients. Most pacemakers are on demand, in which the stimulation of the heart is based on the dynamic demand of the circulatory system. Others send out a fixed rate of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tachycardia-dependent Bundle Branch Block
A tachycardia-dependent bundle branch block is a defect in the conduction system of the heart, and is distinct from typical bundle branch blocks due to its reliable, reproducible onset related to an increase in the rate of cardiac contraction. Tachycardia-dependent bundle branch block can prevent both ventricles from contracting efficiently and can limit the cardiac output of the heart. Anatomy The human heart is a four-chambered organ responsible for the distribution of blood throughout the body. While every physiological effort is made to ensure that such a vital organ can operate continuously without error, sometimes a pathological situation arises and the function of the heart is compromised. One such pathology arises when the electrical signal propagated throughout the heart (responsible for the heart's highly organized contractions) is hindered, resulting in a degradation of said conduction. This is referred to as a bundle branch block and is seen clinically as rate-dependen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
First Degree AV Block
First-degree atrioventricular block (AV block) is a disease of the electrical conduction system of the heart in which electrical impulses conduct from the cardiac atria to the ventricles through the atrioventricular node (AV node) more slowly than normal. First degree AV block does not generally cause any symptoms, but may progress to more severe forms of heart block such as second- and third-degree atrioventricular block. It is diagnosed using an electrocardiogram, and is defined as a PR interval greater than 200 milliseconds. First degree AV block affects 0.65-1.1% of the population with 0.13 new cases per 1000 persons each year. Causes The most common causes of first-degree heart block are AV nodal disease, enhanced vagal tone (for example in athletes), myocarditis, acute myocardial infarction (especially acute inferior MI), electrolyte disturbances and medication. The medications that most commonly cause first-degree heart block are those that increase the refractory ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trifascicular Block
Trifascicular block is a problem with the electrical conduction of the heart, specifically the three fascicles of the bundle branches that carry electrical signals from the atrioventricular node to the ventricles. The three fascicles are one in the right bundle branch, and two in the left bundle branch the left anterior fascicle and the left posterior fascicle. A block at any of these levels can cause an abnormality to show on an electrocardiogram The most literal meaning of trifascicular block is complete heart block: all three fascicles are blocked. A second, and clinically distinct, definition of trifascicular block is a circumstance in which right bundle branch block (RBBB) and left bundle branch block occur in the same patient, but at distinct points in time. For example, a patient that is found to have a RBBB one day and a LBBB another can be said to have "alternating bundle branch blocks". In this context, because all three fascicles show evidence of block at different p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bifascicular Block
Bifascicular block is a conduction abnormality in the heart where two of the three main fascicles of the His/Purkinje system are blocked. Most commonly, it refers to a combination of right bundle branch block (RBBB) and either left anterior fascicular block (LAFB) or left posterior fascicular block (LPFB), with the former being more common. Some authors consider left bundle branch block (LBBB) to be a technical bifascicular block, since the block occurs above the bifurcation of the left anterior and left posterior fascicles of the left bundle branch. Diagnosis Diagnostic criteria: Clinically, bifascicular block presents with one of two ECG patterns: Right bundle branch block (RBBB) with left anterior fascicular block (LAFB), manifested as left axis deviation (LAD). RBBB and left posterior fascicular block (LPFB), manifested as right axis deviation The electrical axis of the heart is the net direction in which the wave of depolarization travels. It is measured using an ele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Left Posterior Fascicular Block
A left posterior fascicular block (LPFB), also known as left posterior hemiblock (LPH), is a condition where the left posterior fascicle, which travels to the inferior and posterior portion of the left ventricle, does not conduct the electrical impulses from the atrioventricular node. The wave-front instead moves more quickly through the left anterior fascicle and right bundle branch, leading to a right axis deviation seen on the ECG. Definition The American Heart Association has defined a LPFB as: * Frontal plane axis between 90° and 180° in adults * rS pattern in leads I and aVL * qR pattern in leads III and aVF * QRS duration less than 120 ms The broad nature of the posterior bundle as well as its dual blood supply makes isolated LPFB rare. See also * Left bundle branch block * Left anterior fascicular block Left anterior fascicular block (LAFB) is an abnormal condition of the left ventricle of the heart, related to, but distinguished from, left bundle branch block (LBBB) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Left Anterior Fascicular Block
Left anterior fascicular block (LAFB) is an abnormal condition of the left ventricle of the heart, related to, but distinguished from, left bundle branch block (LBBB). It is caused by only the left anterior fascicle – one half of the left bundle branch being defective. It is manifested on the ECG by left axis deviation. It is much more common than left posterior fascicular block. Mechanism Normal activation of the left ventricle (LV) proceeds down the left bundle branch, which consist of three fascicles, the left anterior fascicle, the left posterior fascicle, and the septal fascicle. The posterior fascicle supplies the posterior and inferoposterior walls of the LV, the anterior fascicle supplies the upper and anterior parts of the LV and the septal fascicle supplies the septal wall with innervation. LAFB — which is also known as left anterior hemiblock (LAHB) — occurs when a cardiac impulse spreads first through the left posterior fascicle, causing a delay in activation of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
